Cloning material from other skin tex

pixelquack

I'd like to clone bits from one skin mats set onto another. Now, the Base Color part alone, that'd be easy, fire up Gimp and clone away. But what if the bit affects bump/normals, too, so the question is:

How can I repeat the same clone process for just that bit? I am thinking rather than cloning generate an opacity map in Gimp and then merge the visible bit into the original: 

Mask out the Base Color bit I want, Merge with original, then repeat for all affected, use same Opacity Mask on bump, copy, merge, Mask on normals, copy, merge...

Doable, but if anybody knows a faster method I'd take it.